Field of the Invention
This invention relates generally to solar control coatings and, in one particular embodiment, to a solar control coating having increased absorbance and asymmetrical reflectance.
Technical Considerations
Solar control coatings are known in the fields of architectural and automotive transparencies. These solar control coatings block or filter selected ranges of electromagnetic radiation, such as in the range of solar infrared or solar ultraviolet radiation, to reduce the amount of solar energy entering the vehicle or building. This reduction of solar energy transmittance helps reduce the load on the cooling units of the vehicle or building. In automotive applications, the transparency (such as a windshield) is typically required to have a relatively high visible light transmittance, such as greater than 70 percent, to allow passengers to see out of the vehicle. For architectural applications, the visible light transmittance can be lower. In some architectural applications, it may be desirable to have a reflective outer surface so as to decrease visibility into the building to retain as much privacy as possible, while still allowing visible light to enter the building and also allowing the workers inside the building to see out. Also, these transparencies are typically tempered or heat treated for increased safety.
In one known architectural transparency, a heat strengthened glass substrate is coated with a solar control coating having an absorber material, such as a nickel-chromium alloy material (e.g., Inconel®), to absorb visible light to darken the window. This transparency also includes a relatively thick, continuous, infrared reflective metal layer to reflect solar energy, such as solar infrared energy. However, a problem with this known transparency is that the glass substrate must be cut to a desired shape and tempered before the coating is applied. If the coating is applied before the glass substrate is tempered, the resultant coating becomes hazy during the high temperature processings required for the tempering process. This haze is aesthetically undesirable.
It would be desirable to be able to apply a solar control coating onto non-tempered glass sheets and ship the glass sheets to a manufacturer who could then cut the sheets to a desired size for a particular job and then temper or heat treat the cut pieces without adversely impacting upon the aesthetic or solar control properties of the resultant transparency.